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Crape myrtles (Lagerstroemia indica) grow in U.S. Department of Agriculture plant hardiness zones 7 through 9, but some varieties or hybrids may have a slightly differing hardiness, according to Fine Gardening. Crape myrtles are available in tree or bush form, based on the cultivar. Depending on your climate, there are two times of the year that you can do a heavy, annual pruning of your crape myrtles. Other types of trimming depend on the plant itself.

February to March

Late winter or early spring, after the last frost, is usually the time to do any major pruning of crape myrtles. The plants are dormant in the winter, and flowers will only appear on new growth, so pruning in February or March encourages the plant to grow new, flower-producing branches. If you live in a colder area, waiting until the worst of winter is over before pruning helps protect the plant from being damaged by cold temperatures, according to the United States National Arboretum. Trees or bushes left intact through the winter also look better than heavily pruned crape myrtles.

Late Fall

Some people prune off dead wood and cut branches from their crape myrtles late in the fall before the first frost and after the last of the blooms have faded. This should only be done if you live in the mildest areas of the plant's hardiness zones. The University of California Sonoma County Master Gardeners warn that a warm period after pruning could fool the tree into producing new growth, which could become severely damaged after the cold weather for winter finally sets in. The United States National Arboretum recommends never pruning in late fall because the cut surfaces of the crape myrtle could sustain serious cold injury, especially in the coldest reaches of the USDA plant hardiness zones where these plants grow.

Pruning

For annual pruning, you simply need to remove any wood on the plant that could cause a problem, or trim it to control its height. Always use sterilized cutting tools, such as loppers, saws or hand pruners. Remove crossing or dead branches. Cut any suckers you notice at the bottom of the tree or bush. Thin out the main trunks to an odd number between three and seven, cutting the rest down to the ground. Trimming branches in the crown that block out sunlight from the center of the plant or grow in the same area as other branches will help maintain a healthy crape myrtle and help it to avoid powdery mildew.

Pollarding

When pruning crape myrtles avoid what is known as pollarding. This refers to cutting of the major branches down to the knuckles. Doing so can weaken the plant, according to Santa Barbara Garden Designs. Excessive pruning also causes the crape myrtle to produce thin, twiggy branches upward from the location of the cut. Some people pollard crape myrtles to encourage heavy blooming. While this is a result of severely cutting back the plant, the resulting blooms can be so heavy that they cause their supporting branch to bend over. A healthy crape myrtle should have upright branches that easily support their flowers.

After Blooming

Santa Barbara Garden Design recommends removing blooms once they have faded, as well as any seed pods you see. This encourages the tree or bush to grow more flowers. The timing for this trimming depends on when your particular variety first blooms.

Choose Citation Style

Hessong, Athena. "When Is the Best Time to Trim Crape Myrtle Bushes & Trees?" Home Guides | SF Gate, http://homeguides.sfgate.com/time-trim-crape-myrtle-bushes-trees-44490.html. 15 December 2018.

Hessong, Athena. (2018, December 15). When Is the Best Time to Trim Crape Myrtle Bushes & Trees? Home Guides | SF Gate. Retrieved from http://homeguides.sfgate.com/time-trim-crape-myrtle-bushes-trees-44490.html

Hessong, Athena. "When Is the Best Time to Trim Crape Myrtle Bushes & Trees?" last modified December 15, 2018. http://homeguides.sfgate.com/time-trim-crape-myrtle-bushes-trees-44490.html

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